Aerated food products, such as creams, cream alternatives, ice cream, confectionery and bakery fillings are well known. In order to achieve a satisfactory aerated food product with a good overrun and/or firmness emulsifier systems are applied in these products. However the emulsifiers applied sofar, resulting in acceptable products are based on known emulsifier systems such as lecithins, mono-and diglycerides, DATA-esters, polyglycerolesters, etc. Some of these systems are natural, others have to be synthesized, however none of them are known as having benificial health effects.
Therefore we studied whether we could find systems that could replace above known emulsifier systems in aerated products while taking over a number of their benificial effects and adding a number of health benefits.
This study resulted in the finding that the application of shea sterol concentrates in aerated food products could combine both beneficial effects. Shea sterol concentrates being concentrates of shea sterols as present in shea oil, so having the same chemical composition as the sterols in shea oil.
From a number of literature references it is known that sterols present in natural oils can have plasma cholesterol lowering effects. E.g. Weststrate c.s. in Eur. J. clin. Nutr. 52, 1998, p334-343 or Seetharamaiah c.s. in J. Food Science and Techn. 23(1986), p.270-273 and Rukmini c.s. in J. Amer. College of Nutrition 10(1991), p.593-601 disclose the health benefits of oryzanol, i.e. rice bran oil sterols, the main component of oryzanol being cycloartenol. i.e. a 4,4-dimethylsterol with the structure as given in Rukmini""s article. In above references it is also disclosed that oryzanol has serum cholesterol lowering effects. Similar effects have also been disclosed for other plant sterols, c.f.WO 92/19640 and Kochhar, Prog.Lipid Res.22, (1983) p.161-188. The most active forms are according to the literature sito-sterol(=a 4-desmethylsterol) or hydrogenated derivatives thereof.
In particular the sterols wherein the 3-OH group is present in esterified form are mentioned as active.
It should be understood that the term xe2x80x9csterolxe2x80x9d covers 4-desmethylsterols, 4-monomethylsterols and 4.4-dimethylsterols, as defined in Kochhar. This definition includes free sterols, ie having a free 3-hydroxy, group and esterifired sterols, ie sterols having an ester group. derived from fatty acids or phenolic acids at the 3-position.
A problem related with the commercial use of these sterols is the fact that isolation or concentration of the sterols from natural sources is a difficult process. One of the problems indicated e.g. in Kochhar and in Seetharamaiah is that a treatment wherein a refining is applied, using physical means like a solid absorbent or steam easily will result in a deterioration of the sterols, sothat in stead of performing a concentration of the sterols a product is obtained with a lower or maximum the same sterol concentration as present in the starting material. Other concentration techniques, like distillation fail as well, because the natural oils contain a number of components, such as mono- and diglycerides, which cannot be separated from the sterols by distillation techniques, because the partial vapor pressures of these components are very similar.
Although Kochhar gives an extensive overview of the different sterols present in different natural oils it remained a problem to obtain concentrates of useful sterols in concentrations high enough to enable a commercial application of these products.
Shea sterols mainly consist of alpha-amyrin, beta-amyrin, butyrospermol and lupeol, which are all 4,4-dimethylsterols. We found that concentrates of shea-sterols perform very well, when applied in aerated products.
Therefore our invention concerns in the first place concentrates of shea-sterols, in particular concentrates of sterols in glycerides, wherein the concentrate contains at least 12.5 wt %, preferably at least 15 wt %, most preferably at least 20 wt % of shea sterols.
One of the advantages of our novel concentrates is that the shea-sterols are present in a form that is chemically identical with the sterols, as present in shea oil. Preferred concentrates are concentrates, wherein the shea sterols comprise substantial amounts of 4,4-dimethylsterols, in particular selected from the group consisting of alpha-amyrin, beta-amyrin, butyrospermol and lupeol. In particular concentrates, wherein the shea sterols consist for more than 50 wt %, preferably for more than 65 wt %, most preferably for more than 75 wt % of 4,4-dimethylsterols perform very well.
The shea sterol concentrates can be applied as such, or as a blend with other triglycerides either being triglycerides derived from shea oil or triglycerides not akin to the sterol present in the concentrate. So blends of sterols and triglycerides wherein the blend comprises at least 12.5 wt % of shea sterols and at least 20 wt % of triglycerides with a composition different from shea oil are also part of our invention. Examples of sources for the other triglycerides are liquid oils, such as soybean oil, corn oil, sunflower oil, rapeseed oil, the high oleic derivatives of these oils, but also hardened/fractionated oils, such as soybean oil; hard-soybean oil; h-soybean oil midfraction; palm oil; palmolein; palm midfraction; palm kerneloil; hard palm kernel oil; palm kernel olein.
The sterol concentrates can be applied in aerated (whippable) food products or foodproducts that can be aerated and wherein a fat phase and a water phase is present. Examples thereof being whippable creams, ice cream, and confectionery or bakery fillings. The concentration of the shea sterol concentrate in the food products can range from 1 to 30 wt %, based on total product. In general this will mean that on fat 1-50 wt % of shea-sterols will be present.
Our invention further concerns a process for the concentration of shea sterols by performing the following steps:
(i) selecting a shea oil or shea oil fraction, comprising:
(a) partial glycerides, present in an amount of Xa-wt %
(b) triglycerides, present in an amount of Xb-wt %
(c) shea sterols, present in an amount of Xc-wt % and
(d) free fatty acids and/or other volatile components, present in an amount of Xd-wt %
(ii) subjecting this shea oil or shea oil fraction to an enzymic hydrolysis, such that
(1) the amount of component (a) is reduced from Xa to 0-0.95Xa
(2) the amount of component (b) is maintained or reduced from Xb to 0-Xb wt %
(3) the shea sterols (c) are substantially not converted and
(4) the amount of fatty acids and/or other volatile components (d) is increased from Xd to  greater than 1.05Xd
(iii) the components (d) and (b) are removed by one or more physical separation methods and a concentrate of shea sterols with more than 12.5 wt % sterols is recovered.
In above process the value of Xa in our starting material preferably is 0.5-85 wt %, the value of Xb is preferably 0.1-94 wt %, the value of Xc is preferably 0.1-90 wt % and the value of Xd is preferably 0.05-60 wt %, it should however be obvious that the total of Xa-Xd never can be more than 100 wt %, so that the compounds a-d are not always present in the preferred amounts simultaneously.
The enzymic hydrolysis can be performed as a hydrolysis using enzymes specific for the hydrolysis of mono- and diglycerides, sothat these partial glycerides are converted to free fatty acids and glycerol, which compounds easily can be separated from the shea sterols and the triglycerides by physical separation methods. Alternatively higher concentrations of the shea sterols in the concentrate can be obtained if the total starting material is first subjected to a partial enzymic hydrolysis using an enzyme that can hydrolyse all kinds of glycerides present. The resulting reaction mixture will be enriched in free fatty acids,partial glycerides and glycerol. This crude reaction mixture will now be subjected to the enzymic treatment with the enzyme specific for the removal of partial glycerides. The reaction mix resulting from this treatment again will contain components which easily can be separated by physical separation means, such as distillation.
It is of course also possible to perform a one-step hydrolysis using an enzyme or enzyme mixture that can hydrolyze mono-, di- and triglycerides.
By above process shea sterol concentrates can be obtained that contain 12.5-100 wt %, in particular 15-80, more particular 25-70 wt % of sterols.
Shea oil is known to contain about 4 wt % of total sterols, whereas this amount can be as high as 12 wt % for shea oil olein fractions. Therefore these materials are excellent starting materials for the preparation of concentrates that contain high levels of the shea sterols.
As stated above the reaction mixture resulting from the enzymic treatment will contain appreciable amounts of free fatty acids, glycerol and in general triglycerides, in addition to the sterols. The free fatty acids and the glycerol are relatively volatile compounds in this mixture and can be removed by physical separation processes, that do not affect the chemical sterol composition negatively. Examples of such processes are distillation processes, in particular distillation processes under vacuum. On a commercial scale an example of such a process is molecular distillation under reduced pressure.